Polycarbonate-polysiloxane copolymers and methods for preparing the same have been widely studied for many years. In general, polycarbonate-polysiloxane copolymers have been prepared by interfacial polymerization processes. For example, U.S. Pat. No. 5,530,083 discloses an interfacial phosgenation process in which an aromatic dihydroxy compound, phosgene and a catalyst react with diorganopolysiloxane having terminal hydroxyaryl groups. However, this process uses an environmentally hazardous chlorinated solvent.
U.S. Pat. No. 4,994,532 discloses a technique for preparing a polycarbonate-polysiloxane copolymer by melt blending a polydimethylsiloxane having carboxylic acid functional groups with a polycarbonate resin. Further, U.S. Pat. No. 5,194,524 discloses a technique for preparing a copolymer by reaction and extrusion of a siloxane compound having at least one secondary amine group and a polycarbonate resin in a conventional extruder. According to the '524 patent, a polysiloxane having secondary amine functional groups is more effective in the reaction and extrusion process than a polysiloxane having primary amine functional groups because a primary amine has relatively low hydrolysis stability. However, the copolymers can have low temperature impact strength and mechanical strength even though the process is simple and can be performed in a conventional melt extruder.